Implantable device for the sustained release of a polypeptide

ABSTRACT

Described herein are implantable devices, formulations and methods of making implantable devices for the release of a polypeptide from an implantable device, and methods of use thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application No.61/075,625, filed Jun. 25, 2008, incorporated herein by reference in itsentirety.

BACKGROUND

The sustained release of active agents, e.g., exenatide, is known to beof value. In particular, long-term drug delivery has been shown to beeffective in obtaining constant serum levels and in improving patientcompliance.

Hydrogel membranes may be used for sustained delivery of activecompounds. There are several theories regarding the mechanism of solutediffusion in hydrogels. The hydrogels that have been described have someporosity due to the network structure of the crosslinked polymer chains,which allow smaller molecules to diffuse through the structure. The sizeof the pores varies depending upon the hydrogel chemical composition andthus its degree of hydration. The hydrogels described in the art,however, are not particularly well adapted for delivery of largemacromolecules, including bioactive proteins useful for the therapeutictreatment of humans and animals.

There is a need for delivery devices that provide controlled delivery oftherapeutically effective amounts of bioactive polypeptides, which canbe utilized in the treatment of a variety of diseases and pathologicalconditions in humans and animals.

SUMMARY

Described herein are devices, methods and reagents for the controlledrelease of bioactive polypeptides, including, for example, exenatide,and for the preparation of implantable devices useful for the controlledrelease of such polypeptides. Described herein are also devices, methodsand reagents useful for treating particular diseases or disorders.

One embodiment is directed to an implantable device for the sustainedrelease of a polypeptide, comprising: a) a homogeneous copolymer matrixthat, in a hydrated state, forms a hydrogel with an equilibrium watercontent value ranging from about 20% to about 85%, wherein thehomogeneous copolymer matrix further comprises a release agent of amolecular weight of at least about 1000 Daltons; and b) a solidformulation comprising a polypeptide, wherein the solid formulation issubstantially encased within the homogeneous copolymer matrix. In aparticular embodiment, the release agent comprises a non-ionicsurfactant, e.g., one selected from the group consisting of: Brij 35,polyoxyetheylene(20)sorbitan trioleate, Tween 20, Tween 80, Vitamin ETPGS, and combinations thereof. In a particular embodiment, theimplantable device has an outer surface area of about 350 mm² or greaterwhen in a dry state, e.g., from about 350 mm² to about 600 mm². In aparticular embodiment, the implantable device has an outer surface areaof about 500 mm² or greater when in a hydrated state, e.g., from about500 mm² to about 800 mm². In a particular embodiment, the polypeptidecomprises a GLP-1 analogue, e.g., exenatide. In a particular embodiment,the homogeneous copolymer is formed using a formulations of Table 2. Ina particular embodiment, the solid formulation comprises about 98%exenatide and about 2% stearic acid.

One embodiment is directed to a method of delivering a polypeptide to asubject in a sustained release manner, the method comprising insertingan implantable device beneath the subject's skin, wherein theimplantable device comprises a homogeneous copolymer matrix comprising arelease agent with a molecular weight of at least about 1000 Daltons,and a solid formulation comprising a polypeptide, wherein the solidformulation is substantially encased within the matrix. The device canbe inserted in a dry or hydrated state. In a particular embodiment, theimplantable device provides a sustained release of the polypeptide overa period of at least about two months. In a particular embodiment, therelease agent comprises a non-ionic surfactant, e.g., one selected fromthe group consisting of: Brij 35, polyoxyetheylene(20)sorbitantrioleate, Tween 20, Tween 80, Vitamin E TPGS, and combinations thereof.In a particular embodiment, the implantable device has an outer surfacearea of about 350 mm² or greater when in a dry state, e.g., from about350 mm² to about 600 mm². In a particular embodiment, the implantabledevice has an outer surface area of about 500 mm or greater when in ahydrated state, e.g., from about 500 mm² to about 800 mm². In aparticular embodiment, the polypeptide comprises a GLP-1 analogue, e.g.,exenatide. In a particular embodiment, the homogeneous copolymer isformed using a formulations of Table 2. In a particular embodiment, thesolid formulation comprises about 98% exenatide and about 2% stearicacid. In a particular embodiment, the subject is diabetic or in need ofglycemic control.

One embodiment is directed to a method of treating a diabetic subject,comprising inserting an implantable device under the diabetic subject'sskin, wherein the implantable device comprises a homogeneous copolymermatrix comprising a release agent with a molecular weight of at leastabout 1000 Daltons, and a solid formulation comprising a polypeptideselected from the group consisting of: a GLP-1 analog, exenatide,liraglutide, and analogs thereof, wherein the solid formulation issubstantially encased within the copolymer matrix. In a particularembodiment, the device provides a release on a daily basis an effectiveamount of the polypeptide over a period of at least about three months,at least about six months or at least about twelve months.

One embodiment is directed to a method of treating a subject in need ofglycemic control, comprising inserting beneath a hypoglycemic orhyperglycemic subject's skin an implantable device comprising ahomogeneous copolymer matrix, and a solid formulation comprising apolypeptide selected from the group consisting of exenatide,liraglutide, and analogues thereof, which is substantially encasedwithin said matrix; and allowing said device to release on a daily basisan effective amount of said polypeptide over a period of at least aboutthree months, at least about six months or at least about twelve months.In a particular embodiment, the matrix includes a release agent having amolecular weight of at least about 1000.

One embodiment is directed to a method of manufacturing an implantabledevice, wherein the implantable device can deliver a therapeuticpolypeptide agent to a subject, and the release of the therapeuticpolypeptide agent from the implantable device can be modulated byvarying the components or the amounts of the components of theimplantable device, the method comprising: a) mixing one or morepolymerizable monomeric substances; b) adding one or more substancesselected from the group consisting of: an excipient, a wetting agent, anon-ionic surfactant, an organic solvent, an alcohol, a reducing agent,an oxidizing agent and an aqueous solvent; and c) subjecting the mixtureto conditions that cause the one or more polymerizable monomericsubstances to polymerize in the presence of the one or more components,thereby forming the implantable device. In a particular embodiment, theone or more polymerizable monomeric substances comprises one or morecompounds selected from the group consisting of: 2-hydroxyethylmethacrylate, ethyleneglycol dimethacrylate, and trimethylolpropanetrimethacrylate. In a particular embodiment, the mixture furthercomprises one or more components selected from the group consisting of:benzoin methyl ether, Perkadox 16, and isopropyl alcohol. In aparticular embodiment, the rate of release of the therapeuticpolypeptide can be modulated. In a particular embodiment, the mixture isplaced into a mold prior to being subjected to a polymerization step. Ina particular embodiment, the polymerization step is initiated byultraviolet irradiation. In a particular embodiment, the method(s) ofmanufacturing an implantable device further comprise charging or loadingthe implantable device with a desired amount of a therapeuticpolypeptide agent. In a particular embodiment, the therapeuticpolypeptide agent comprises a GLP-1 analog, e.g., exenatide. In aparticular embodiment, the therapeutic polypeptide agent is combinedwith a wetting agent to form a solid formulation prior to being chargedinto the implantable device. In a particular embodiment, the solidformulation comprises about 98% exenatide and about 2% stearic acid.

One embodiment is directed to an implantable device that is formed usinga mixture of about 78.72% HEMA, about 0.40% EGDMA, about 0.79% Vitamin ETDGS, about 0.24% BME, about 0.08% P-16, about 9.89% water and about9.89% isopropyl alcohol.

One embodiment is directed to an implantable device that is formed usinga mixture of about 78.72% HEMA, about 0.40% EGDMA, about 0.79% Vitamin ETDGS, about 0.24% BME, about 0.08% P-16 and about 19.78% water.

One embodiment is directed to an implantable device that is formed usinga mixture of about 68.97% HEMA, about 0.35% EGDMA, about 0.69% Vitamin ETDGS, about 0.21% BME, about 0.07% P-16, about 14.85% water and about14.85% isopropyl alcohol.

One embodiment is directed to an implantable device that is formed usinga mixture of about 68.97% HEMA, about 0.35% EGDMA, about 0.69% Vitamin ETDGS, about 0.21% BME, about 0.07% P-16 and about 29.71%.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a graph showing in vitro exenatide release from fourformulations as described in Example 7. HEMA: 2-hydroxyethylmethacrylate; EGDMA: ethyleneglycol dimethacrylate; TMPTMA:trimethylolpropane trimethacrylate; BME: benzoin methyl ether; P-16:Perkadox 16; IPA: isopropyl alcohol.

DETAILED DESCRIPTION

Before the present compositions and methods are described, it is to beunderstood that they are not limited to the particular molecules,compositions, methodologies or protocols described, as these may vary.It is also to be understood that the terminology used in the descriptionis for the purpose of describing the particular versions or embodimentsonly, and is not intended to limit the scope of the present invention,which will be limited only by the appended claims. The terms used hereinhave meanings recognized and known to those of skill in the art,however, for convenience and completeness, particular terms and theirmeanings are set forth below.

The singular forms “a”, “an”, and “the” include plural reference unlessthe context clearly dictates otherwise. Unless defined otherwise, alltechnical and scientific terms used herein have the same meanings ascommonly understood by one of ordinary skill in the art. Although anymethods and materials similar or equivalent to those described hereincan be used in the practice or testing of embodiments described herein,the preferred methods, devices, and materials are now described. Allpublications mentioned herein are incorporated by reference to theextent they support the present invention. Nothing herein is to beconstrued as an admission that the invention is not entitled to antedatesuch disclosure by virtue of prior invention.

As used herein, the term “about” means plus or minus 10% of thenumerical value of the number with which it is being used. For example,about 50% means in the range of 40%-60%.

“Controlled-release formulation” refers to a formulation designed toconsistently release a predetermined, therapeutically effective amountof drug or other active agent such as a polypeptide or a syntheticcompound over an extended period of time, with the result being areduction in the number of treatments necessary to achieve the desiredtherapeutic effect. As described herein, a controlled formulationdecreases the number of treatments necessary to achieve the desiredeffect. The controlled-release formulations achieve a desiredpharmacokinetic profile in a subject, preferably commencement of therelease of the active agent substantially immediately after placement ina delivery environment, followed by consistent, sustained, preferablyzero-order, substantially zero-order, or near-zero order release of theactive agent.

As used herein, the term “controlled-release” includes thepredetermined, consistent release of active agent from the dosageformulation at a rate such that a therapeutically beneficial blood levelbelow toxic levels of the active agent is maintained over a period, forexample, of at least about two months, about six months or more (e.g.,up to about two years).

The terms “patient” and “subject” mean all animals including humans.Examples of patients or subjects include humans, cows, dogs, cats,goats, sheep and pigs.

The term “pharmaceutically acceptable salts, esters, amides, andprodrugs” as used herein refers to those carboxylate salts, amino acidaddition salts, esters, amides, and prodrugs of the compounds of thepresent invention that are, within the scope of sound medical judgment,suitable for use in contact with the tissues of patients without unduetoxicity, irritation, allergic response and the like. Their use iscommensurate with a reasonable benefit/risk ratio, and is effective fortheir intended use. Zwitterionic forms, where possible, can also beused. The compounds described herein can exist, for example, inunsolvated and solvated forms with pharmaceutically acceptable solventssuch as, for example, water, ethanol and the like. In general, thesolvated forms are considered equivalent to the unsolvated forms for thepurposes of the present invention.

The term “prodrug” refers to compounds that are rapidly transformed invivo to yield the parent compounds of the above formula, for example, byhydrolysis in blood. A discussion is provided in T. Higuchi and V.Stella, “Pro-drugs as Novel Delivery Systems,” Vol. 14 of the A.C.S.Symposium Series, and in Bioreversible Carriers in Drug Design, ed.Edward B. Roche, American Pharmaceutical Association and Pergamon Press,1987, both of which are incorporated herein by reference in theirentireties.

The term “salts” refers to the relatively non-toxic, inorganic andorganic acid addition salts of compounds of the present invention. Thesesalts can be prepared in situ during the final isolation andpurification of the compounds or by separately reacting the purifiedcompound in its free base form with a suitable organic or inorganic acidand isolating the salt thus formed. Representative salts include theacetate, hydrobromide, hydrochloride, sulfate, bisulfate, nitrate,acetate, oxalate, valerate, oleate, palmitate, stearate, laurate,borate, benzoate, lactate, phosphate, tosylate, citrate, maleate,fumarate, succinate, tartrate, naphthylate mesylate, glucoheptonate,lactobionate and laurylsulphonate salts, and the like. These can includecations based on the alkali and alkaline earth metals, such as sodium,lithium, potassium, calcium, magnesium, and the like, as well asnon-toxic ammonium, tetramethylammonium, tetraethylammonium,methylamine, dimethylamine, trimethylamine, triethylamine, ethylamineand the like (See, for example, S. M. Barge et al., “PharmaceuticalSalts,” J. Pharm. Sci., 1977, 66:1-19, which is incorporated herein byreference in its entirety).

The terms “active agent” or “drug” as used herein includes any agentthat can be delivered to produce a clinically useful result. For thepurposes described herein, the active agent or drug is a polypeptidethat can be delivered from an implantable device to produce the desiredclinical effect. The active agents, whether in solid or liquid form,have sufficient solubility or miscibility in an aqueous system to renderthem capable of being released through the hydrogel membranes into thedelivery environment. Active agents include, but are not limited to,synthetic as well as natural polypeptides and their analogues, andinclude those polypeptides that are physiologically or pharmacologicallyactive (“bioactive polypeptide”) and produce a localized or a systemiceffect in animals. Polypeptide active agents, for example, can haveglucoregulatory effects such as lowering blood glucose levels, improvingglucose control, suppressing pancreatic glucagon release, delayinggastric emptying, and/or reducing appetite in an animal or human.

As used herein, the term “polypeptide” refers to a polymer in whichmonomer amino acids (“amino acid residues”) are joined together throughpeptide or disulfide bonds. It also refers to either a full-lengthnaturally occurring amino acid sequence, to an analogue of a naturallyoccurring sequence, or to a fragment thereof between, for example, about8 to about 500 amino acids in length. The polypeptides of the inventioncan be naturally occurring or synthetic. Unnatural amino acids, forexample, beta-alanine, phenyl glycine and homoarginine, can be includedwithin a polypeptide sequence. All of the amino acids of thepolypeptides used in the present invention can be either the D- orL-optical isomer. Peptide nucleic acids (PNAs) are also included withinthe scope of the invention. A PNA is a DNA-mimic having apolypeptide-like inorganic backbone composed of, for example,N-(2-aminoethyl)glycine units, with an organic base (A, G, C, T or U)attached to the glycine nitrogen via a methylene carbonyl linker(Nielsen, P. et al., Bioconjug. Chem., 5:3-7, 1994). Polypeptide activeagents suitable for the methods and devices of the present invention canbe, for example, from about 3 amino acids (aa) in length to about 200 aain length; from about 8 aa to about 150 aa in length; from about 15 aato about 100 aa in length; from about 25 aa to about 75 aa in length;from about 30 aa to about 50 aa in length; or from about 39 aa to about50 aa in length. In some embodiments, the polypeptide is about 5 aa toabout 20 aa in length, or about 5 aa to about 12 aa. In yet otherembodiments, the polypeptide is about 30 aa to about 50 aa in length, orabout 39 aa to about 50 aa in length. Suitable polypeptide active agentsinclude those having a molecular weight in the range of about 500Daltons to about 100,000 Daltons, and, in particular, to those havingmolecular weights in the range of about 500 Daltons to about 50,000Daltons, about 500 Daltons to about 25,000 Daltons, and about 500Daltons to about 10,000 Daltons, as well as those having moleculeweights in the range of about 1,000 Daltons to about 8,000 Daltons,about 1,000 Daltons to about 6,000 Daltons, about 2,000 to about 5,000Daltons, or about 3,000 Daltons to about 5,000 Daltons.

“Treatment” refers to the administration of medicine or the performanceof medical procedures with respect to a patient, either for prophylaxis(prevention) or to cure the infirmity or malady in the instance wherethe patient is afflicted.

A “therapeutically effective amount” is an amount sufficient todecrease, prevent or ameliorate the symptoms associated with a medicalcondition.

Described herein are implantable delivery devices composed of homogenousporous hydrogels that are suited for delivery of polypeptides and theiranalogues, and methods of making the devices. The devices, whenimplanted into a subject, provide sustained delivery of polypeptideactive agents to the subject.

Hydrogels allow for the diffusion of molecules in aqueous environments.It has been hypothesized that there are three classes of water inhydrogels, including, “Z” water, which is bound to the polymer matrix,“Y” water, which is partially affected by the polymer matrix, and bulkor “X” water, which is unaffected by the polymer matrix. This theory wasexpanded with the notion that the diffusion of hydrophilic solutesthrough hydrogel membranes depends on molecular size of the solute andwater content of the hydrogel and that the permeation takes place viathe bulk water (Refojo, M. and Leong, F., J. Polymer Sci.: PolymerSymp., 66:227-237, 1979; Kim, S. et al., ACS Symp. Ser., 127:347-359,1980).

As described herein, the inclusion of certain liquid diffusion enhancers(which remain in liquid form following polymerization) in the mixture ofpolymerizable materials, permits the creation of a hydrogel having poresthat are evenly dispersed and of a size to enhance diffusion of largermolecules through the network structure of the crosslinked polymerchains of the hydrogel. Additional characteristics and advantages ofthese liquid diffusion enhancers are described herein.

This invention may be especially useful in cases where the polypeptidesare “pegylated,” as this process significantly increases the originalmolecular weight by the polyethylene glycol (PEG) portion. As usedherein, “pegylation” refers to the practice of adding PEG to apolypeptide active agent. This practice has been found to stabilizepolypeptides by decreasing their recognition by the immune system andimproving their half life.

One or more polypeptide active agents are embedded or substantiallyencased in a cartridge made of a biologically inert polymer matrix toform a delivery device suitable for sustained release of the polypeptidewhen implanted into a subject. The cartridges used in the devices aretypically cylindrical hollow tubes made by extrusion, injection molding,reaction injection molding, compression molding, or spin-castingdepending on the type of polymer used. Such cylindrical hollow tubes mayhave one or two open ends. Following molding or casting, the polypeptideactive agent is introduced into the hollow core, or reservoir of thecartridge. Additional liquid material that is polymerizable may beintroduced into the core opening and cured to seal the cartridge.

For those embodiments in which the cartridge is produced using a mold,one or more release agents are optionally present in the polymer matrixof the cartridge to aid in removal of the cartridge from the mold. Therelease agent is typically combined with the polymerizable material thatultimately forms the cartridge prior to introducing the polymerizablematerial into the mold.

Prior to implantation, the implantable formulations can be optionallyhydrated or “primed” for a predetermined period of time. Priming canenable the active ingredient to begin to infiltrate and saturate thewalls of the hydrogel and potentially begin to leach out of the hydrogelprior to implantation depending upon the amount of time the implant isprimed. A primed implant begins to release active ingredientsubstantially upon implantation, and can result in a peak release of thedrug shortly after implantation. In contrast, little to no priming canresult in substantially no release of the active ingredient uponimplantation for a period of time until the implant becomes hydrated andthe active ingredient begins to be released. These primingcharacteristics depend on the specific formulations being used.

Depending upon the types of active ingredient, hydrophilic orhydrophobic, the appropriate conditioning and priming media are chosen.Water-based media are preferred for hydrophilic actives and oil-basedmedia are preferred for hydrophobic actives. Alternatively, certainimplants do not need to be primed prior to implantation. In someinstances, priming improves delivery of the active agent in a controlledfashion, but in other instances, priming prior to implantation in asubject does not affect delivery in a way to justify the added time andhassle required for priming the implant.

The hydrating liquid useful in the practice of the invention istypically a liquid simulating the environment in which the activecompound will be released, e.g., body fluid, sterile water, tear fluid,physiological saline solution, phosphate buffer solution and the like.While liquids other than water are useful as the hydrating liquid, thedegree to which a hydrophilic membrane is hydrated is referred to as its“water content.”

The priming and conditioning of the drug delivery devices involves theloading of the drug into the polymer that surrounds the reservoir, andthus prevent loss of the active before the actual use of the implant.The conditions used for the conditioning and priming step depend on theactive agent, the temperature and the medium in which they are carriedout. The conditions for the conditioning and priming can be the same insome instances.

The conditioning and priming step in the process of the preparation ofthe drug delivery devices is performed to obtain a determined rate ofrelease of a specific drug. The conditioning and priming step of theimplant containing a hydrophilic drug can be carried out in an aqueousmedium, e.g., in a saline solution. For hydrophobic drugs, the mediumcan be a plasma-like medium, including, for example, cyclodextrin. Theconditioning and priming steps are carried out by controlling threespecific factors, namely the temperature, the medium and the period oftime.

A person skilled in the art would understand that the conditioning andpriming step of the drug delivery device is affected by the medium inwhich the device is placed.

The temperature used to condition and prime the drug delivery device canvary across a wide range of temperatures, but, in some embodiments, 37°C., is used.

The time period used for the conditioning and priming of the drugdelivery devices can vary from about an hour, about 1 to about 12 hours,about 2 to about 24 hours, about a single day, or up to several weeks,e.g., 6 weeks, depending on the release rate desired for the specificimplant or drug.

A person skilled in the art will understand the steps of conditioningand priming the implants, where appropriate or necessary, is to optimizethe rate of release of the drug contained within the implant. As such, ashorter time period spent on the conditioning and the priming of a drugdelivery device can result, for example, in a lower rate of release ofthe drug compared to a similar drug delivery device that has undergone alonger conditioning and priming step. Without priming, however, it wasunexpectedly found that effective release occurred over a longer periodof time (e.g., 28 weeks and beyond), and lower serum concentrations ofthe active ingredient were found to have ameliorative effects.

The temperature in the conditioning and priming step can also affect therate of release in that a lower temperature results in a lower rate ofrelease of the drug contained in the drug delivery device when comparedto a similar drug delivery device that has undergone a treatment at ahigher temperature. Similarly, in the case of aqueous solutions, e.g.,saline solutions, the sodium chloride content of the solution determinesthe release rate for the drug delivery device. More specifically, alower content of sodium chloride can result in a higher rate of releaseof drug when compared to a drug delivery device that has undergone aconditioning and priming step where the sodium chloride content washigher.

To identify the location of the implant, radiopaque material can beincorporated into the delivery device by inserting it into the reservoiror by making it into end plug to be used to seal the cartridge.

Methods for the preparation of the hydrogels are described in detail inU.S. Pat. No. 6,361,797, for example, which is incorporated by referenceherein in its entirety. Materials that are utilized in the reactionmixture used to form the matrix, including the monomers, co-monomers,diffusion enhancers, and the like, are preferably biologicallycompatible and biologically inert, e.g., have no significant effect onanimals or the human body. The materials for some embodiments havepreviously been approved for use in animals by the USDA and/or for usein humans by the FDA, or equivalent agencies. Such prior regulatoryapproval, however, is not a requirement. It is well within the skill ofthose in the art to select suitable materials.

Polymerizable material useful in the manufacture of the homogenousporous hydrogels of the devices include a wide variety of hydrophilic,ethylenically unsaturated compounds, in particular, hydrophilic monomerssuch as the monoester of an acrylic acid (e.g., methacrylic acid) with apolyhydroxy compound having an esterifiable hydroxyl group and at leastone additional hydroxyl group such as the monoalkylene and polyalkylenepolyols of methacrylic acid and acrylic acid, e.g., 2-hydroxyethylmethacrylate and acrylate, diethylene glycol methacrylate and acrylate,propylene glycol methacrylate and acrylate, dipropylene glycolmethacrylate and acrylate, glycidyl methacrylate and acrylate, glycerylmethacrylate and acrylate, and the like; the 2-alkenamides, e.g.,acrylamide, methacrylamide, and the like; the N-alkyl and N,N′-dialkylsubstituted acryl-amides and methacrylamides such asN-methylmethacrylamide, N,N′-dimethylmethacrylamide, and the like;N-vinylpyrrolidone; the alkyl-substituted N-vinylpyrrolidones, e.g.,methyl substituted N-vinylpyrrolidone; N-vinylcaprolactam; thealkyl-substituted N-vinylcaprolactam, e.g., N-vinyl-2-methylcaprolactam,N-vinyl-3,5-dimethylcaprolactam, and the like. Other suitable monomersinclude those described in U.S. Pat. No. 4,303,066. In one desiredembodiment, the co-monomers are a mixture formed of at least two of theabove hydrophilic monomers. Alternatively, the co-monomers are a mixtureformed of at least one hydrophilic monomer and at least one hydrophobicmonomer.

In some embodiments, the hydrophilic monomer is 2-hydroxyethylmethacrylate (HEMA). Suitable co-monomers useful in the inventioninclude HEMA and N,N′-dimethylacrylamide or HEMA and methacrylic acid.Still other suitable monomers and co-monomers can be readily selectedfrom among those known in the art.

Useful crosslinking agents that can be included in the polymerizablereaction medium include, for example, the polyethylenically unsaturatedcompounds having at least two polymerizable ethylenic sites, such as thedi-, tri- and tetra-ethylenically unsaturated compounds, in particular,the tri-unsaturated crosslinking agents with/without the di-unsaturatedcrosslinking compounds, for example, divinylbenzene, ethylene glycoldimethacrylate and diacrylate, propylene glycol dimethacrylate anddiacrylate, and the di-, tri- and tetra-acrylate or methacrylate estersof the following polyols; triethanolamine, glycerol, pentaerythritol,1,1,1,-trimethylolpropane; and others. Other suitable crosslinkingagents may be readily selected by one of skill in the art.

Diffusion enhancers can be mixed with the polymerizable materials.Mixing can be done in a way to achieve uniform distribution anddispersion (e.g., by mixing, spinning, etc.) in the reaction medium,however the diffusion enhancers(s) but do not themselves polymerize.Rather, following the polymerization reaction, pores containing thesediffusion enhancers are formed within the polymerized hydrogel material.Thus, the diffusion enhancers are liquids at room and/or bodytemperatures both prior to and following the polymerization reaction.These compounds include, for example, methyl alcohol, ethyl alcohol,propyl or isopropyl alcohol, allyl alcohol, tetrahydrofurfuryl alcohol,cyclohexyl alcohol, diethylene glycol, polyethylene glycols, glycerol,acetone, ethylene glycol monomethyl ether, ethylene glycol monoethylether, ethylene glycol monobutyl ether, glyceryl isopropylidene etherdioxane, tetrahydrofuran, ethyl acetate, dimethyl sulfoxide and water.Water soluble micronized solids can also be used for this purpose. Suchwater soluble micronized solids include, for example, any solid thatwill dissolve to leave pores within the polymerized hydrogel material,including, e.g., sugar, baking soda, and sodium chloride. Otherdiffusion enhancers can be selected according to known properties by oneof skill in the art, particularly from among those compounds that aremiscible with the starting monomers and are soluble in water.

Unlike formulations described by others, the diffusion enhancersdescribed herein do not interfere with homogeneity during spin casting,and thus permit the formation of more homogenous hydrogels. Theseadvantages are particularly apparent when spin or rotational casting isused to prepare the articles of the invention.

One or more release agents are optionally included in the polymerizablereaction medium. In general, release agents are compounds capable ofallowing effective release of a molded article from a mold. For thedevices of the present invention, the release agent is typicallycombined with the polymerizable reaction medium prior to introducing thepolymerizable material to a mold.

Release agents suitable for use in the implantable devices are safe forintroduction into a patient, do not adversely react with the polymer ofthe molded article, for example, by causing weakening of the structureof the article, and optionally protect the polymer cartridge fromadverse effects of sterilization. Without being bound by theory, it isbelieved that higher molecular weight release agents provide improvedrelease characteristics over those provided by lower molecular weightrelease agents. Release agents accordingly can have a molecular weight(MW) in excess of about 1000. In other embodiments, the release agentshave a MW in excess of about 1200, from about 1000 to about 2000, orbetween about 1200 and about 1800.

Suitable release agents include non-ionic surfactants. In someembodiments, for example, the release agent is Vitamin E TPGS. Vitamin ETPGS is an abbreviation for D-α-tocopheryl (Vitamin E) polyethyleneglycol 1000 succinate. Non-ionic surfactants release agents provideexcellent release properties and are non-reactive with the moldedarticle while providing a safety profile that is suitable for implants.These release agents additionally can act as antioxidants or freeradical scavengers and, therefore, prevent or reduce adverse effects onthe molded article associated with sterilization of the molded article,especially sterilization methods that can generate free radicals,including irradiation methods. In particular embodiments, the releaseagent dissolves in a desired monomer mixture. A hydrophilic monomermaterial, such as, for example combinations of HEMA, HPMA and HBMA, canbe used in combination with an amphiphilic release agent, such as, forexample, Vitamin E TPGS, during the molding process.

Non-ionic surfactants are known in the art, and may generally consist ofa polyethylene glycol hydrophilic tail and a lipophilic head. ForVitamin E TPGS, for example, the lipophilic head is tocopherol succinateand for Triton X-100 it is an isooctylphenyl group. Non-ionicsurfactants can be characterized by several parameters, such as, forexample, hydrophilic-lipophilic balance (HLB), which relates the size ofthe polyethylene glycol tail to the lipophilic head; critical micelleconcentration (CMC), which is the concentration of surfactant at whichmicelles form; and MW, which describes the size of the hydrophilic andlipophilic portions relative to other surfactants with similarproperties. Additionally, CMC is an indication of the surface activityof the surfactant, and a low CMC is indicative of a more stable micellebecause of stronger binding forces. The Table below lists severalsurfactants and their physical properties.

TABLE 1 Surfactants Name ~MW HLB CMC (mM) Triton X-100 625 13.5 0.2-0.9Vitamin E TPGS 1513 13 0.1 Triton X-114 537 12.4 0.2 Brij 35 1200 16.90.05-0.1  Tween 20 1228 16.7  0.06 Tween 80 1310 15  0.012 Sucrosemonolaurate 525 ~8 0.2

Additional release agents for use in combination with the implantabledevices include, but are not limited to, polyoxyethylene(2) stearylether, sorbitan monolaurate, polyoxyethylene(5)nonylphenyl ether,polyoxyetheylene(20)sorbitan trioleate,polyoxyethylene(10)isooctylphenyl ether, and the like, or combinationsof these release agents.

In certain embodiments, the release agent is a polyoxyethylene ester offatty acids or other hydrophobic compounds. These compounds are known inthe art and include a polyoxyethylene tail and a saturated orunsaturated hydrophobic head. The hydrophobic moiety of variousembodiments can include any aromatic group containing moiety orpolycyclic aromatic moieties such as, for example, a phenol, a catechol,a resorcinol, a hydroquinone, a tocopherol, Vitamin E, and the like andcan be isoprenoid or non-isoprenoid. The side chains associated withthese aromatic moieties can be of any length and can additionallyinclude any number of double bonds and/or substitutions. Non-ionicsurfactants, for example, can include, but are not limited to, naturallyoccurring or commercially manufactured tocopherols including anyisoform, racemate, or chemically modified derivative, such as, Vitamin ETPGS. Tocopherols can also include oxidation products of tocopherols,such as the oxidation products of α-tocopherol, tocopherol quinones,tocopherol hydroquinones, epoxytocopherols, and nitrotocopherols.

A polymerizable mixture is formed, for example, by mixing co-monomerswith a crosslinker and a diffusion enhancer, e.g., about 50% to about95%, about 60% to about 90%, or about 75% to about 85%, by weight, ofthe polymerizable monomers can be included in the mixture. Generally,the crosslinker is added in an amount in the range of about 0.1% toabout 5%, about 0.5% to about 3%, and about 1%, by weight, of themixture. The diffusion enhancers are generally included in an amount ofabout 1% to about 50%, about 5% to about 40%, about 10% to about 30%, orabout 20%, by weight, of the mixture.

The polymerizable mixture can be polymerized to produce a polymer orcopolymer matrix. The polymerization reaction can be carried out in bulkor with an inert solvent. Suitable solvents include, but are not limitedto, water; organic solvents such as water-soluble lower aliphaticmonohydric alcohols as well as polyhydric alcohols, e.g., glycol,glycerine, dioxane, etc., and mixtures thereof.

Compounds useful in the catalysis of the polymerizable ethylenicallyunsaturated compounds include the free radical compounds and/orinitiators of the type commonly used in vinyl polymerization such as theorganic peroxides, percarbonates, hydrogen peroxides, and alkali metalsulfates. Illustrative examples include, but are not limited to, cumenehydroperoxide, t-butyl hydroperoxide, benzoyl peroxide,bis(4-t-butylcyclohexyl) peroxydicarbonate, hydrogen peroxide,2,4-dichlorobenzoyl peroxide, acetyl peroxide, di-n-propylperoxydicarbonate, di-t-butyl peroxide, di-sec-butyl peroxydicarbonate,ammonium sulfate, potassium sulfate, and sodium sulfate. In oneembodiment, the catalyst is effective at a moderately low temperaturesuch as, for example, at about 20-80° C. (e.g., tert-butyl peroctoate,benzoyl peroxide, and di(secbutyl) peroxydicarbonate).

A conventional redox polymerization catalyst can also be employed.Polymerization of the ethylenic compounds can be effected, for example,using radiation, e.g., ultraviolet, X-ray, gamma radiation, microwave orother known forms of radiation. An example of a catalyst for ultravioletcure is benzoin methyl ether. Catalysts and/or initiators and/orradiation are employed in a catalytically effective amount to optimizethe polymerization reaction. The advantage of redox initiation is thatthe reaction occurs at reasonable rates at low temperatures, e.g., 0° C.to 50° C., and can be effected in the presence of water. A large numberof reductant-oxidant pairs producing free radicals is known in the art.Examples include sodium bisulfate and ammonium persulfate, sodiumthiosulfate and potassium persulfate, and the like. Catalysts and/orinitiators and/or radiation are employed in a catalytically effectiveamount to optimize the polymerization reaction.

The polymerization reaction can be conducted in a mold or polymerizationcolumn to form a cartridge that is used to construct an implantabledevice. Cartridges can be prepared from the polymerizable mixture usingany method known in the art, such as, for example, extrusion, injectionmolding, reaction injection molding, compression molding orspin-casting.

To form a cartridge, the monomer(s), or polymerizable material preparedas described above is introduced to a mold or polymerization column. Themolds and polymerization columns described herein have interior surfacesthat are cylindrical, such that cross-sectional areas of the interior ofthe column are circular in shape and about equal in diameter and smooth.Molds and polymerization columns of various embodiments can be made ofany suitable material, such as, for example, plastics, including, butnot limited to, polyethylene, polypropylene, and polystyrene; metal;glass; and the like. In some embodiments, the column can be fabricatedfrom a material that allows electromagnetic radiation to pass into thepolymerization zone of the column, and in certain embodiments, glass,such as Pyrex™, is used to make the mold or polymerization column.

In some embodiments, cartridges are made by centrifugally-casting orspin-casting. In some of these embodiments, the cartridge is prepared bypreparing a polymerization column or mold of appropriate size with oneextremity of the column being closed and the other extremity beingopen-ended and adapting the polymerization column or mold for rotationabout its longitudinal axis; introducing a monomer to the column ormold; rotating the column or mold about its longitudinal axis andmaintaining it substantially parallel to the ground at a speedsufficient to displace the monomer radially outward along the interiorsurfaces of the column or mold such that the monomer assumes acylindrical configuration with a core; polymerizing the monomer toconvert it to a solid molded article having a concentric cylindricalcore; and recovering the article, or reservoir cartridge. The speed atwhich the mold or polymerization column is rotated can vary, dependingupon the size of the cartridge being made, the type of polymerizablematerial being used, and the effectiveness of the release agent. Forexample in some embodiments, the rotational speed may be from less thanabout 1000 rpm to greater than 6000 rpm, and in certain embodiments, therotational speed may be about 2150 rpm.

The polymerizable material in the cartridge can also be optionallycured. Curing can be carried out any one of a number of methods known inthe art and for any period of time depending on the type ofpolymerizable material used and the size of the cartridge beingprepared. For example, when the polymerizable material has achieved thepredetermined shape, the mold or polymerization column can be irradiatedwith ultraviolet light for a period of time, such as, for example, fromabout 1 to about 10 minutes, to initiate polymerization of thepolymerizable material. The cartridge can then undergo thermal curingand annealing. In some embodiments, the cartridge is thermally cured forabout 60 minutes at a temperature up to about 100° C. followed bypost-curing for about 30 minutes at a temperature up to about 120° C.and annealing for about 30 minutes at about up to 130° C., followed bygradual cooling to ambient temperature (about 25° C.). The curedcartridge is removed from the mold or polymerization column, washed toremove excess release agent and/or to extract pore formers, and polishedto achieve a smooth, unscored surface. After shaping and polishing theclosed end of the cartridge to a oval-like cylindrical profile, there isobtained small, cylindrically shaped objects having smooth, unscoredcylindrical surfaces. Typical dimensions of the cartridges are asfollows: internal radius 0.98 mm; external radius 1.3 mm; length 25 mm.

In some embodiments in which a cylindrical cartridge is used to form theimplantable device, the length of the hydrated cartridge can be fromabout 5 mm to about 60 mm, and the external diameter may be from about1.5 mm to about 5 mm. While the release agents can be used in any sizeimplant, in some embodiments, the release agents are used in thepreparation of larger implant devices. The length of a hydratedcartridge prepared using a non-ionic surfactant release agent can befrom about 40 to about 60 mm, for example, and the external diameter canbe from about 3 to about 5 mm. In some embodiments, the length of ahydrated cartridge is 45 to 60 mm, and the external diameter is from 3.5to 4.8 mm. Without wishing to be bound by theory, non-ionic surfactantrelease agents can overcome the surface tension in molds used duringpreparation of cartridges while allowing the cartridge to be readilyreleased from the mold. In certain embodiments, a larger cartridge canbe used for large animals or livestock, such as, for example, sheep,cows, goats, cattle, and the like because larger animals can tolerateimplantation of larger drug delivery devices.

The external surface area of the implant, e.g., the external surfacearea of the polymer cartridge or hollow tube, can vary. In someembodiments, the surface area of the polymer cartridge can have asurface area of from about 350 mm² to about 1500 mm². Hydrated implantsand xerogel (e.g., non-hydrated, or dry) implants have differentdimensions and, therefore, different surface areas. In some embodiments,the release agents are used in the preparation of larger implantdevices. A xerogel, non-hydrated, or dry implant, for example can have asurface area of about 350 mm² or greater. Alternatively, a xerogel,non-hydrated, or dry implant can have a surface area of from about 350mm² to about 1500 mm², or from about 350 mm² to about 600 mm². The dryimplant, for example, can have a surface area from 378 mm² to 660 mm².Additionally, a hydrated implant can have a surface area of about 500mm² or greater. The hydrated implant alternatively can have a surfacearea of from about 600 mm² to about 1500 mm², or from about 600 mm² toabout 800 mm². As used herein, the term “hydrated implant” refers toimplants having a water content of 5% (wt), or greater, and are thussoft and flexible. As used herein, “dry implant” refers to implants thatare rigid and inflexible, having a water content less than 5% (wt), insome embodiments, and less than 1% (wt), in other embodiments.

The implantable devices can be inserted subcutaneously in a human orother animal by any suitable means known in the art, e.g., byperforation (for subcutaneous implantation) or by other means, e.g.,open surgery (U.S. Pat. No. 5,266,325, which discloses examples ofmethods and devices that can be used to implant the devices; the entirecontents of U.S. Pat. No. 5,266,325 are herein incorporated byreference). The implantable device can be inserted subcutaneously in thehuman or animal by perforation, for example. In addition, more than onedevice can be implanted into the human or animal at the same time, e.g.,substantially simultaneously, so that multiple devices are present asimplants in the human or animal. Thus, in some embodiments, at least onedevice is implanted into the human or animal. Alternatively, multipledevices can be implanted sequentially, so that only one device ispresent in the human or animal at any one time. Such devices arecharacterized by a length of 10-50 mm, or less (e.g., 6-9 mm), anexternal diameter of 2-5 mm, or less (e.g., 1.5-1.9 mm). The dimensionsof the cartridge can vary outside of the limits stated above depending,in particular, on the medical application involved. Animals such assheep, cows, goats, cattle, and large animals, in general, can tolerateimplantation by perforation of the larger-dimensional implantabledevices.

Smooth, unscored cylindrically shaped objects of various lengths, e.g.,up to 25 cm and longer, can also be prepared in accordance with theteachings herein. Such objects, in a hydrated state or plasticized witha non-toxic, biocompatible material, can be formed into desired shapes,e.g., a ring shape, for use as pessaries, surgical implants, etc. Yetother devices can be prepared using techniques known to those of skillin the art.

The implantable devices are prepared by introducing a pre-determinedamount of one or more polypeptide active agents, optionally combinedwith a pharmaceutically acceptable carrier, into the reservoir, or core,of a cartridge obtained by the methods described above.

Polypeptides suitable for use as active agents in the implantabledevices include, but are not limited to, growth factors, interferons,interleukins, granulocyte macrophage colony stimulating factor (GM-CSF),neurotrophic factors and the like. Additional examples of polypeptidesinclude exendins (including, e.g., exendin-4, exenatide, andliraglutide); amylin analogues (e.g., pramlintide); corticotropinreleasing factor (CFR) and CFR receptor antagonists (including, e.g.,astressin); β-endorphins (including, e.g., β-lipotropin) andγ-endorphins; endostatins; galanins; gastric inhibitory peptide;ghrelins (e.g., ghrelin and obestatin); glucagon; incretins, includingglucagon-like polypeptides; pancreatic polypeptides; polypeptidesproduced in the ileum or colon (including, e.g., PYY₃₋₃₆); adipokines(including, e.g., omentin); leptin; oxyntomodulin; pituitary adenylatecyclase activating peptides (PACAP); somatostatin analogues or mimicssuch as octreotide; polypeptides that favor energy expenditure(including, e.g., melanocortin, α-MSH, and polypeptides that signalthrough the POMC (pro-opiomelanocortin) and CART (cocaine- andamphetamine-regulated transcript) pathways); and analogues and fragmentsthereof.

Further examples of suitable polypeptide active agents include thosehaving antiretroviral activity, e.g., HIV fusion inhibitors such asenfuvirtide (marketed as Fuzeon® by Roche, and disclosed in U.S. Pat.No. 5,464,933, the entire contents of which are herein incorporated byreference(Tyr-Thr-Ser-Leu-Ile-His-Ser-Leu-Ile-Glu-Glu-Ser-Gln-Asn-Gln-Gln-Glu-Lys-Asn-Glu-Gln-Glu-Leu-Leu-Glu-Leu-Asp-Lys-Trp-Ala-Ser-Leu-Trp-Asn-Trp-Phe;SEQ ID NO:1)), and analogues and fragments thereof. Polypeptides alsoconsidered suitable for use in the implantable devices include growthhormone and growth hormone releasing factors (GHRF), growth hormonereleasing peptides (GHRPs), and analogues and fragments thereof.Examples of growth hormone releasing peptides (GHRPs) include, e.g.,GHRP-6, and GHRP-2 (e.g., Pralmorelin (under development by KakenPharmaceuticals), which is disclosed in U.S. Pat. No. 7,008,927).

Additional examples of polypeptides that can be used in the implantabledevices include calcitonin and calcitonin gene related polypeptides, aswell as parathyroid hormone (PTH) (including, e.g., teriparatide(marketed as Forteo® by Eli Lilly and Co., and disclosed in U.S. Pat.No. 6,770,623, the entire contents of which are herein incorporated byreference(Ser-Val-Ser-Glu-Ile-Gln-Leu-Met-His-Asn-Leu-Gly-Lys-His-Leu-Asn-Ser-Met-Glu-Arg-Val-Glu-Trp-Leu-Arg-Lys-Lys-Leu-Gln-Asp-Val-His-Asn-Phe;SEQ ID NO:2)), and analogues and fragments thereof.

For yet additional specific examples of polypeptides suitable for use inthe devices and methods described herein, see American Peptide Company,Inc., Peptide catalog 2006-2007, inparticular, pages 119, 171, 175, 207,211, 217, 219, 227, 315, 317, and 329, the contents of which are hereinincorporated by reference. See also the following U.S. patents andpublished patent applications: U.S. Patent Publication Nos. 20050287320;20070010656; 20060293232; 20060233747; 20060148713; 20060122106;20060035836; 20060030528; 20040002454; 20030036504; and 20020141985; andU.S. Pat. Nos. 7,271,238; 7,259,136; 7,220,721; 7,153,825; 7,118,737;7,115,569; 7,105,489; 7,101,853; 7,056,887; 7,008,927; 6,969,480;6,942,264; 6,872,700; 6,770,623; 6,602,694; 6,579,851; 6,417,164;6,143,718; 6,087,334; 5,686,411; and 5,464,933. The entire contents ofeach of these U.S. patents and published patent applications is hereinincorporated by reference in its entirety.

In some embodiments, the polypeptide active agent is an incretinmimetic, e.g., a GLP-1 analogue such as an exendin (e.g., exendin-4, orexenatide (disclosed in U.S. Pat. No. 6,872,700, the entire contents ofwhich are herein incorporated by reference(His-Gly-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Leu-Ser-Lys-Gln-Met-Glu-Glu-Glu-Ala-Val-Arg-Leu-Phe-Ile-Glu-Trp-Leu-Lys-Asn-Gly-Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser;SEQ ID NO:3), and marketed as Byetta® by Amylin Pharmaceuticals, Inc.)),or a fragment or analogue thereof. For example, in some embodiments, thepolypeptide active agent is the GLP-1 analogue Liraqlutide (having thechemical structureArg(34)Lys(26)-(N-epsilon-(gamma-Glu(N-alpha-hexadecanoyl))-GLP-1(7-37)(e.g., as disclosed in WO 2007/028394).

In other embodiments, the polypeptide active agent is an amylin mimetic,e.g., pramlintide (disclosed in U.S. Pat. No. 5,686,411, the entirecontents of which are herein incorporated by reference(Lys-Cys-Asn-Thr-Ala-Thr-Cys-Ala-Thr-Gln-Arg-Leu-Ala-Asn-Phe-Leu-Val-His-Ser-Ser-Asn-Asn-Phe-Gly-Pro-Ile-Leu-Pro-Pro-Thr-Asn-Val-Gly-Ser-Asn-Thr-Tyr;SEQ ID NO:4); pramlintide acetate in an injectable form is marketed asSymlin® by Amylin Pharmaceuticals, Inc.), or a fragment or analoguethereof.

The polypeptide active agent can be present in free form or in the formof a pharmaceutically acceptable salt, such as, for example, an acetatesalt, pamoate salt, gluconate salt, lactate salt, or hydrochloride salt.

In various embodiments, the polypeptide active agents are combined withone or more pharmaceutically acceptable carriers to produce solutions,emulsions, suspensions, and the like that are suitable for use in theimplantable devices. Methods of formulating the polypeptide active agentand the pharmaceutically acceptable carrier are known to those of skillin the art, and various pharmacologic references can be consulted forguidance. See, for example, Remington's Pharmaceutical Sciences, Osol,A., ed., Mack Publishing Company, Easton, Pa. (1980).

Suitable pharmaceutically acceptable carriers may be in the form ofsuspending media, solvents, aqueous systems, and solid substrates ormatrices, as described in U.S. Pat. No. 6,361,797. Suspending media andsolvents useful as the carrier include, for example, oils such assilicone oil (particularly medical grade), corn oil, castor oil, peanutoil and sesame oil; condensation products of castor oil and ethyleneoxide containing about 30 to 35 moles of ethylene oxide per mole ofcastor oil; liquid glyceryl triesters of a lower molecular weight fattyacid; lower alkanols; glycols; and polyalkylene glycols.

Aqueous systems include, for example, sterile water, saline, dextrose,dextrose in water or saline, and the like. The presence of electrolytesin the aqueous systems may tend to lower the solubility of thepolypeptide active agent in them.

Solid substrates or matrices include, for example, starch, gelatin,sugars (e.g., glucose), natural gums (e.g., acacia, sodium alginate,carboxymethyl cellulose, hydroxypropylcellulose), and the like. Thecarrier can also contain adjuvants or additional excipients such aspreserving, stabilizing, wetting and emulsifying agents, diluents andthe like, including, for example, magnesium stearate, stearic acid, andthe like. Additional examples of adjuvants and excipients are known tothose of skill in the art.

The polypeptide active agent can be combined with a pharmaceuticallyacceptable carrier that is a solid substrate or matrix (e.g.,hydroxypropylcellulose), and is optionally combined with one or moreadditional excipients, to form a solid formulation comprising thepolypeptide. In those embodiments in which the polypeptide is in a solidformulation, the polypeptide is also in solid form, e.g., a powder.Solid forms of polypeptides can be obtained using methods known in theart, including, but not limited to, precipitation, crystallization,spray drying, air drying, freeze drying (lyophilization), vacuum drying,and open drying. For example, in some embodiments, solid polypeptide isprepared by lyophilizing an aqueous solution of the polypeptide. Thepowdered polypeptide can be in a granular or particulate form. If thepolypeptide has an amorphous structure or has a particle size that isheterogeneous and poorly defined, it can be further processed to producea particulate, granular powder using any suitable method known in theart, including, but not limited to, milling the solid polypeptide (see,e.g., U.S. Pat. Appl. Publ. No. 2006/0067911), or spray drying asolution of the solid polypeptide to produce a granular powder.

In some embodiments, the powdered polypeptides are in a granular orparticulate form having particles of well-defined size (e.g., particlesfalling within a defined size range). Methods for reduction of particlesize are known in the art and include, for example, milling (using,e.g., ball, rod, hammer, colloid or fluid-energy mills). The particlesize can be controlled using standard techniques well known to those ofordinary skill in the art. Suitable particle sizes are generally about500 microns or less in diameter. The polypeptide particles can range insize from about 10 microns to about 500 microns. It will be appreciatedthat the particle sizes specified above are exemplary and that particlesizes that vary slightly from those mentioned above, e.g., ±20%, such as±10% or ±5%, are encompassed by the use of the term “about.”

The implantable devices are formed by introducing into the core of thedevice, for example, into the cartridge, one or more polypeptide activeagents, optionally combined with one or more carriers to form apolypeptide formulation, and then partially filling the core. In someembodiments, after the core has been partially filled, a layer of aninert material, such as Teflon tape, can be placed on top of the activeagent, and the void in the core above the covering can be sealed toprevent leakage into or out of the cartridge. The seal can be formed byfilling the void with a polymerizable material, such as a polymerizablematerial used to make the cartridge, and polymerizing the polymerizablematerial to form a plug that seals the opening of the cartridge. In someembodiments, the polymerizable material used to form the plug can be theliquid polymerizable material used to make the cartridge and may nothave an equilibrium water content value exceeding the equilibrium watercontent value of the hydrophilic cartridge, upon maximum hydration. Inother embodiments, the polymerizable material can be of similarcomposition but with a higher hydrophilicity than the liquidpolymerizable material employed in the fabrication of the cartridge.

In some embodiments, a plug for a cartridge having a core filled withpolypeptide active agent and covered with teflon tape, can be made byfirst cleaning and slightly increasing the internal surface area of thecore above the polypeptide agent by careful reaming the open end of thecartridge with an appropriate reamer. The reamed surface area can thenbe cleaned with a sufficient amount of a mono or polyhydric alcohol,such as, for example, ethanol, causing a slight swelling of the surfaceof the cartridge. Using a fine needle syringe, a small amount of theliquid polymerizable material can be injected into the cartridge fillingthe core to the top. The polymerizable material can then be polymerizedby positioning the cartridge so that its longitudinal axis isperpendicular to the ground, rotating the cartridge on using forexample, a lathe at a relatively low speed, such as, about 100 rpm toabout 200 rpm, and exposing the cartridge to ultraviolet light forseveral minutes, for example, 5-10 minutes. In the event the activeagent is sensitive to ultraviolet light, a shield such as, for example,aluminum foil can be used to shield the active compound from theultraviolet light. In general, the curing of the plug should take placeat a temperature that is not detrimental to the drug, for example,ambient temperature. Without wishing to be bound by theory, reaming andcleaning the open end of the cartridge promotes the penetration of thepolymerizable hydrophilic material into the treated surface.

The filled and sealed cartridges can be sterilized by any sterilizationtechnique known in the art, depending on the material used to make thecartridge and the active agent to be delivered. For example, suitablesterilization techniques include, but not be limited to, heatsterilization, radiation sterilization, such as cobalt 60 irradiation,gamma radiation, or electron beams, ethylene oxide sterilization, andthe like. In certain embodiments, agents affixed to the cartridge canact as an antioxidant or free radical scavenger during sterilization toreduce or eliminate the adverse affects of free radicals formed duringsterilization by, for example, irradiation.

The implantable devices can also be readily adapted to delivery ofcombinations of one or more of the various types of polypeptidesdescribed above.

The amount of polypeptide active agent employed in the implantabledevices depends not only on the desired daily dose but also on thenumber of days that dose level is to be maintained. While this amountcan be calculated empirically, the actual dose delivered is also afunction of any interaction with materials and the carrier, if employedin the device. The polypeptide compositions are present in the sustainedrelease compositions in varying amounts, depending upon the effectdesired.

The polymeric matrix of the xerogel implantable device can be hydratedprior to implantation to form the hydrogel, and the device implantedinto a subject in a hydrated state. Alternatively, the implant mayself-hydrate upon implantation as a dry implant, and thus, no hydrationof the implant prior to implantation is necessary.

To form a hydrogel, the polymer matrix must be hydrated, typically byexposure to an aqueous solution or to aqueous media. Upon exposure toaqueous media, the xerogel absorbs the aqueous fluid to become ahydrogel containing pores which are relatively evenly dispersedthroughout the hydrogel matrix. Suitably, the pores formed in thehydrogel range in size from 10 Angstroms (1×10⁻⁹ m) to several microns.Other suitable ranges include from 50 Angstroms to 0.1 microns and from0.1 microns to 1 micron. When the molecule for delivery is amacromolecule, the pore size is suitably over 50 Angstroms. As describedherein, the pores contain diffusion enhancers.

The hydrating liquid used to prepare the hydrogel is typically a liquidsimulating the environment in which the polypeptide active agent will bereleased, e.g., body fluid, sterile water, tear fluid, physiologicalsaline solution, phosphate buffer solution, and the like. While liquidsother than water are useful as the hydrating liquid, the degree to whicha hydrophilic membrane is hydrated is referred to as its “watercontent.”

The hydrogel does not dissolve upon exposure to water, but permits theimbibing of water. When a hydrogel attains it maximum level ofhydration, the water content of the hydrogel is referred to as“equilibrium water content” (EWC). The percent water content of thehydrogel (any state of hydration) is determined as described in U.S.Pat. No. 6,361,797.

A hydrogel described herein can have an EWC value in the range of fromabout 20% to about 90%, about 35% to about 85%, or about 50% to about80%, as desired. Advantageously, the hydrogels of the invention have anincreased EWC value, as compared to the equivalent hydrogels withoutdiffusion enhancers. Such improvements in EWC value correspond with anincrease in release rate.

It is the ability of the hydrogel to swell with water, and thus,increase the area between the cross-links, which permits the passage ofthe polypeptide active agents. By controlling the level of hydration, itis possible to control the rate of passage of these active agentsthrough the hydrogel matrix into the surrounding environment, e.g., thebody. The use of the diffusion enhancers as described herein facilitatespassage of the polypeptide active agents. More particularly, duringhydration of the hydrogel, the diffusion enhancers leach out of thehydrogel into the surrounding environment, thus permitting the pores tofill with water from the surrounding environment. The presence of thediffusion enhancers as described herein permits the formation of pores,which are larger than those found in their absence. Diffusion enhancersinclude, but are not limited to, saline, isotonic water, and phosphatebuffered saline. These pores provide larger spaces that permit thepassage of macromolecular active agents into the surroundingenvironment.

The hydrogels can be selected to be non-toxic, and once hydrated, tocontain no residual monomers or extractables. Further, the hydrogels arecharacterized by low reactivity, and are sufficiently flexible that theymimic the surrounding tissue. Thus, these hydrogels are well suited foruse in the animal, particularly, mammalian and more particularly, humanbody.

Upon implantation, the devices provide sustained release of thepolypeptide active agent drugs over extended periods of time. This timeperiod can range from several days to a few years, for example, from oneweek to three years depending on the desired administration regimen. Therelease time can be about a week to about 18 months or longer, it beingunderstood that this time factor is variable depending on therate-releasing membrane of choice, its interconnecting pore structure,the active compound of choice, the solubility of the active compound inthe liquid medium, and other considerations known to those skilled inthe art. In some embodiments, the implantable devices provide sustainedrelease of the polypeptide active agent over an extended period of timethat lasts at least one month. In other embodiments, sustained releaseof the polypeptide is provided over an extended period of time lasts atleast two months, at least three months or at least six months. In yetother embodiments, the extended period of time of release of thepolypeptide lasts at least one year.

In some embodiments, the implantable devices described above can be usedin a method of delivering a sustained release of a polypeptide to asubject, allowing the device to release on a daily basis an effectiveamount of the polypeptide over a defined period, e.g., a period of atleast about two months, at least about three months, or at least aboutsix months. For example, in some embodiments, the implantable device canbe used in a method of delivering a sustained release of a polypeptideto a subject in need thereof, the method comprising inserting beneath asubject's skin an implantable device comprising a homogeneous copolymermatrix, including a release agent having a molecular weight (MW) of atleast about 1000, and a solid formulation comprising a polypeptide,which is substantially encased within the matrix; and allowing thedevice to release on a daily basis an effective amount of thepolypeptide over a period of at least about two months.

Methods for determining the release profile (e.g., delay time, releaserate and duration) of a macromolecular composition from the implantabledevices are well known, and include use of the Fick's First Law ofDiffusion. See, e.g., U.S. Pat. No. 5,266,325, which is hereinincorporated by reference.

In some embodiments, the implantable devices provide delayed/sustainedrelease or immediate/sustained release of one or more polypeptides to ananimal. “Delayed/sustained release” is defined as delaying the releaseof the polypeptide active agent until after placement in a deliveryenvironment, followed by a sustained, preferably zero-order, release ofthe polypeptide at a later time. “Immediate/sustained release” isdefined as the commencement of the release of the polypeptide activeagent immediately or soon thereafter after placement in a deliveryenvironment, followed by sustained release of the polypeptide. Otherapplications of the present invention include controlled delivery inindustrial, agricultural and domestic settings.

The implantable devices of the present invention are designed to providesustained release of polypeptide active agents and can be used inmethods of treating various conditions or disorders in humans andanimals depending upon the particular polypeptide active agent employedin the implantable device and the disease, disorder or condition againstwhich the polypeptide is known to be effective.

For example, in some embodiments of the present invention, thepolypeptide active agent is a GLP-1 analogue (e.g., exenatide orliraglutide) that exhibits glucoregulatory effects such as enhancingglucose-dependent insulin secretion by pancreatic beta-cells, loweringblood glucose levels, improving glycemic control, suppressing pancreaticglucagon release, delaying or slowing gastric emptying, and/or reducingappetite in an animal or human, effects all relevant to the treatment ofdiabetes.

Accordingly, the implantable devices described above can be used in amethod of treating diabetes in a human or animal. In some embodiments,the method of treating diabetes in an animal comprises administering aGLP-1 analogue in an implantable device described above that providessustained release of effective therapeutic amounts of the GLP-1 analogueto the human or animal over an extended period of time.

In some embodiments, the implantable devices can be used in a method oftreating a subject suffering from a type of diabetes, comprisinginserting beneath a diabetic subject's skin an implantable devicecomprising a homogeneous copolymer matrix, including a release agenthaving a molecular weight (MW) of at least about 1000, and a solidformulation comprising a GLP-1 analogue polypeptide (e.g., exenatide,liraglutide, and analogues thereof), which is substantially encasedwithin the matrix; and allowing the device to release on a daily basisan effective amount of the polypeptide over a period of time, e.g., atleast about two months, at least about three months, or at least aboutsix months.

In some preferred embodiments, the implantable devices are used toadminister a polypeptide in a method of treating type 2 diabetes.

The implantable devices described above can also be used in othermethods relating to the other glucoregulatory effects of the GLP-1analogue, e.g., in a method of enhancing glucose-dependent insulinsecretion in an animal or human, lowering blood glucose levels in ananimal or human, improving glycemic control in an animal or human,suppressing pancreatic glucagon release in an animal or human, slowinggastric emptying in an animal or human, reducing appetite in an animalor human, and treating obesity in an animal or human. Accordingly, theimplantable devices can also be used, for example, in a method oftreating hyperglycemia, or of treating insulin resistance, or treatingmetabolic syndrome, in a human or animal, the method comprisingadministering a polypeptide in a hydrogel implantable device thatprovides sustained release of effective therapeutic amounts of thepolypeptide to the human or animal over an extended period of time.

In some embodiments, one of the implantable devices can be used in amethod of treating a subject in need of glycemic control, the methodcomprising inserting beneath a hypoglycemic or hyperglycemic subject'sskin an implantable device comprising a homogeneous copolymer matrix,and a solid formulation comprising a GLP-1 analogue polypeptide (e.g.,exenatide, liraglutide, and analogues thereof), which is substantiallyencased within the matrix; and allowing the device to release on a dailybasis an effective amount of the polypeptide over a period of time,e.g., over a period of at least about two months, at least about threemonths, or at least about six months.

Embodiments directed to a method of treating diabetes (e.g., to a methodlowering blood glucose levels, or to a method of improving glycemiccontrol) by administering a GLP-1 analogue such as, for example,exenatide or liraglutide using an implantable device described above,the GLP-1 analogue is administered in an effective daily dose of about10 μg to about 100 μg, or preferably about 10 μg to about 50 μg (e.g.,the implantable device provides sustained release of the GLP-1 analogueat a range of about 10 μg to about 100 μg GLP-1 analogue each day,preferably about 10 μg to about 50 μg per day).

In those embodiments directed to methods of treating certain conditionsor disorders by administering a polypeptide using an implantable devicedescribed above, the polypeptide can be administered in combination withone or more other treatments or other medications that are designed totreat the same condition or disorder. The other treatment or medicationcan be administered by a route and in an amount commonly used, and canbe administered concurrently or sequentially with the polypeptide. Theother medication or treatment can also be administered prior toadministration of the polypeptide.

In those embodiments in which the other treatment or medication isadministered concurrently with the polypeptide, the other treatment ormedication can be administered using the same route of administration asthe polypeptide or using a different route of administration (e.g.,including oral, parenteral (e.g., intramuscular, intraperitoneal,intravenous, intracisternal injection or infusion, subcutanteousinjection, or implant), by inhalation spray, or by nasal, vaginal,rectal, sublingual, or topical routes of administration). The othertreatment or medication can also be formulated together with thepolypeptide, e.g., in the same implantable device, or formulatedseparately using any suitable dosage unit formulation known in the art.

Some embodiments are directed to a method of treating type 2 diabetes(e.g., to a method lowering blood glucose levels, or to a method ofimproving glycemic control) by administering a GLP-1 analogue such asexenatide or liraglutide using an implantable device described above. Insome of these embodiments, the GLP-1 analogue can be administered inconjunction with another medication used to treat diabetes, such aspioglitazone, metformin, a sufonylurea, and/or insulin administered byroutes and in amounts commonly used and known to the skilled clinician.For example, in some embodiments directed to a method of treatingdiabetes (e.g., directed to a method of improving glycemic control), asubject is administered the GLP-1 analogue exenatide using one of thesustained-delivery implantable devices of the invention, while at thesame time receiving daily oral administration of metformin (e.g., in theform of a 500 mg oral tablet of metformin hydrochloride).

In other embodiments, e.g., in those embodiments directed to a method oftreating obesity using an implantable device described above (forexample, by administering an amylin mimetic such as pramlintide), thepolypeptide administered using the implant (e.g., the amylin mimetic)can be administered in conjunction with one or more other agentsdesigned to treat obesity, such as, for example, an oral formulation ofsibutramine (e.g., a 5, 10 or 15 mg capsule of sibutraminehydrochloride, administered daily), a parenteral formulation of leptin(e.g., an injectable formulation), an oral formulation of orlistat(e.g., a 120 mg capsule of orlistat (tetrahydrolipstatin), marketed asXenical® by Hoffmann-La Roche Inc.), an oral formulation of phentermine,an oral formulation of bupropion (e.g., Wellbutrin SR, marketed byGlaxoSmithKlein), or an oral formulation of rimonabant (marketed bySanofi-Aventis in Europe under the name Acomplia).

The following examples are provided to illustrate the invention and donot limit the scope thereof One skilled in the art will appreciate thatalthough specific reagents and conditions are outlined in the followingexamples, modifications can be made which are meant to be encompassed bythe spirit and scope of the invention.

EXEMPLIFICATION Example 1

A monomeric mixture comprised of 94.5% 2-HEMA, 5% propylene glycol and0.5% ethylene glycol dimethacrylate (EGDMA) was prepared. 2-HEMA waspreviously purified by vacuum distillation. To the resulting mixture,0.2% benzoin methyl ether was added and dissolved.

An implant cartridge was initially prepared as described in U.S. Pat.No. 5,266,325. More particularly, the mixture was deoxygenated bybubbling nitrogen through it for 10 minutes. To avoid prematurepolymerization the mixture was shielded from light. One end of apolypropylene tube (65 mm in length and di of 2.5 mm) was plugged with asilicone sealant; the other end of the tube was sealed with a plug madeby injecting a small amount of the above mixture, which was cured undera UV lamp for 5 minutes. Using a syringe filled with the mixture, thesilicone plug was punctured and the tube was filled with the mixture toa height of about 10 mm from the top. The tube was inserted in a lathecollet and spun (spinning axis parallel to the ground) at about 2200rpm. The centrifugal force created by the spinning tube caused theradially outward displacement of the mixture to assume a predeterminedhollow cylindrical liquid configuration (a hollow tube of polymerizableliquid mixture). The spinning tube was then exposed to UV light for 7minutes to polymerize the “liquid tube” to a solid hydrophilic tube(cartridge). The cartridge within the polypropylene tube was post-curedfor 14 hours at 65° C., followed with an additional 40 minutes at 105°C., and annealed at 116° C. for 40 minutes, and then slowly cooled to22° C.

The cartridge was ejected from the tube, inspected for defects, and cutto a length of 30 mm. There was obtained a precisely dimensional plasticcartridge fabricated of crosslinked homogeneous 94.5% HEMA/5%polypropylene glycol/0.5% EDGMA polymer characterized by recurringhydrophilic units. The weight of the cartridge was recorded.

This cartridge is available for filling with a polypeptide active agentby tightly packing it to a 20 mm height. The filled cartridge is weighedagain to determine the weight of active agent. The empty space of thecartridge is filled with the aforesaid monomeric mixture. Part of thecartridge containing the active agent is covered with aluminum foil. Thecartridge is then placed in the lathe and spun slowly (spinning axis ofcartridge parallel to ground) under a UV lamp for 5 minutes to effectpolymerization of the mixture. Post-curing of the polymer plug waseffected by maintaining the cartridge at 50° C. for 18 hours. The endproduct is an implantable device.

Example 2

A monomeric mixture comprised of 92.5% 2-HEMA, 2% methacrylic acid, 5%polyethylene glycol 200 and 0.5% ethylene glycol dimethacrylate wasprepared and processed as in Example 1.

Example 3

A monomeric mixture comprised of 74.5% 2-HEMA, 20%N,N′-dimethylacrylamide (N,N′-DMA), 5% isopropyl alcohol and 0.5%ethylene glycol dimethacrylate was prepared and processed as in Example1.

Examples 4-6

Monomeric mixtures comprised of 2-HEMA and propylene glycol in theratios shown in the Table were prepared and processed as in Example 1.(The concentrations of crosslinker and catalyst remained constant.).

Example 7

The formulations of Table 2 were prepared by first mixing HEMA, EGDMA,Vitamin E, BME and P-16 in the indicated proportions. The appropriatequantities of IPA and/or water were then added.

TABLE 2 Formulation % HEMA % EGDMA % Vit. E % BME % P-16 % Water % IPA A78.72 0.40 0.79 0.24 0.08 9.89 9.89 B 78.72 0.40 0.79 0.24 0.08 19.78 —C 68.97 0.35 0.69 0.21 0.07 14.85 14.85 D 68.97 0.35 0.69 0.21 0.0729.71 —

Pre-determined volumes of the resulting mixtures were dispensed intoglass molds and were subjected to a horizontal spin-casting processwhile being exposed to ultraviolet light. Upon removal of the resultingcured polymer tubes from the molds, the tubes were further dried in avacuum oven. Drug pellets were prepared on a single station tablet pressfrom a blend of 98% exenatide and 2% stearic acid. Drug pellets wereloaded into the dried polymer tubes and the ends sealed with a monomermixture comprised of 99.5% HEMA and 0.5% TMPTMA.

The implants were tested in vitro for exenatide release, and the resultsare shown in the Figure.

Although the present invention has been described in considerable detailwith reference to certain preferred embodiments thereof, other versionsare possible. Therefore the spirit and scope of the appended claimsshould not be limited to the description and the preferred versionscontained within this specification.

1. An implantable device for the sustained release of a polypeptide,comprising: a) a homogeneous copolymer matrix that, in a hydrated state,forms a hydrogel with an equilibrium water content value ranging fromabout 20% to about 85%, wherein the homogeneous copolymer matrix furthercomprises a release agent of a molecular weight of at least about 1000Daltons; and a solid formulation comprising a polypeptide, wherein thesolid formulation is substantially encased within the homogeneouscopolymer matrix.
 2. The implantable device of claim 1, wherein therelease agent comprises a non-ionic surfactant.
 3. The implantabledevice of claim 1, wherein the release agent is selected from the groupconsisting of: Brij 35, polyoxyetheylene(20)sorbitan trioleate, Tween20, Tween 80, Vitamin E TPGS, and combinations thereof.
 4. Theimplantable device of claim 1, wherein the implantable device has anouter surface area of about 350 mm² or greater when in a dry state. 5.The implantable device of claim 4, wherein the implantable device has anouter surface area ranging from about 350 mm² to about 600 mm² when in adry state.
 6. The implantable device of claim 1, wherein the implantabledevice has an outer surface area of about 500 mm² or greater when in ahydrated state.
 7. The implantable device of claim 6, wherein theimplantable device has an outer surface area ranging from about 500 mm²to about 800 mm² when in a hydrated state.
 8. The implantable device ofclaim 1, wherein the polypeptide comprises a GLP-1 (glucagon-likepeptide) analogue.
 9. The implantable device of claim 8, wherein theGLP-1 (glucagon-like peptide) analogue is exenatide.
 10. The implantabledevice of claim 1, wherein the homogeneous copolymer matrix is formedusing a formulation comprising hydroxyethylmethacrylate, ethyleneglycoldimethacrylate, the release agent, water and a lower aliphaticmonohydric alcohol.
 11. The implantable device of claim 10, wherein theformulation is selected from the group consisting of a) about 78.72%HEMA (hydroxyethylmethacrylate), about 0.40% EGDMA (ethyleneglycoldimethacrylate), about 0.79% Vitamin E TPGS, about 0.24% BME (benzoinmethyl ether), about 0.08% P-16 (Perkadox® 16), about 9.89% water andabout 9.89% isopropyl alcohol; b) about 78.72% HEMA, about 0.40% EGDMA,about 0.79% Vitamin E TPGS, about 0.24% BME, about 0.08% P-16 and about19.78% water; c) about 68.97% HEMA, about 0.35% EGDMA, about 0.69%Vitamin E TPGS, about 0.21% BME, about 0.07% P-16, about 14.85% waterand about 14.85% isopropyl alcohol; and about 68.97% HEMA, about 0.35%EGDMA, about 0.69% Vitamin E TPGS, about 0.21% BME, about 0.07% P-16 andabout 29.71% isopropyl alcohol.
 12. The implantable device of claim 1,wherein the solid formulation comprises about 98% exenatide and about 2%stearic acid.
 13. A method of delivering a polypeptide to a subject in asustained release manner, the method comprising inserting an implantabledevice beneath the subject's skin, wherein the implantable devicecomprises a homogeneous copolymer matrix comprising a release agent witha molecular weight of at least about 1000 Daltons, and a solidformulation comprising a polypeptide, wherein the solid formulation issubstantially encased within the matrix.
 14. The method of claim 13,wherein the implantable device is inserted in a dry state.
 15. Themethod of claim 13, wherein the implantable device is inserted in ahydrated state.
 16. The method of claim 13, wherein the implantabledevice provides a sustained release of the polypeptide over a period ofat least about two months.
 17. The method of claim 13, wherein therelease agent comprises a non-ionic surfactant.
 18. The method of claim17, wherein the release agent is selected from the group consisting of:Brij 35, polyoxyetheylene(20)sorbitan trioleate, Tween 20, Tween 80,Vitamin E TPGS, and combinations thereof.
 19. The method of claim 13,wherein the implantable device has an outer surface area of about 350mm² or greater when in a dry state.
 20. The method of claim 19, whereinthe implantable device has an outer surface area ranging from about 350mm² to about 600 mm² when in a dry state.
 21. The method of claim 13,wherein the implantable device has an outer surface area of about 500mm² or greater when in a hydrated state.
 22. The method of claim 21,wherein the implantable device has an outer surface area ranging fromabout 500 mm² to about 800 mm² when in a hydrated state.
 23. The methodof claim 13, wherein the polypeptide comprises a GLP-1 analogue.
 24. Themethod of claim 23, wherein the GLP-1 analogue is exenatide.
 25. Themethod of claim 13, wherein the homogeneous copolymer matrix is formedusing a formulation comprising hydroxyethylmethacrylate, ethyleneglycoldimethacrylate, the release agent, water and a lower aliphaticmonohydric alcohol.
 26. The method of claim 25, wherein the solidformulation comprises about 98% exenatide and about 2% stearic acid. 27.The method of claim 13, wherein the subject is diabetic or in need ofglycemic control.